Capturing an image with a camera equipped with an XY address scanning type image sensor, such as a complementary metal oxide semiconductor (CMOS) image sensor, under illumination of a fluorescent lamp may cause occurrence of brightness non-uniformity or color non-uniformity in the form of stripes in video signals. This phenomenon is called flicker. This occurs due to the fact that a fluorescent lamp connected to a commercial power supply (alternating current) basically repeats blinking on and off with a cycle which is basically twice that of a power supply frequency and also due to the operating principle of an image sensor.
An image with flicker shows brightness variation pattern in the form of stripes extending in the horizontal direction. As one example, upon observing a moving image, stripes flowing up and down will appear. When detection of a region in which motion exists in such an image is performed using the image, flicker is more likely to be detected as the region in which motion exists. An example of an approach for motion detection with the reduced influence of flicker includes Patent Literatures 1 to 3.